1. Field of the Invention
The present invention relates to a position detecting apparatus and a position detecting device thereof, said position detecting apparatus having the capability of detecting more than one position pointing devices simultaneously.
2. Description of the Related Art
U.S. Pat. No. 4,878,553 discloses a position detecting apparatus with a cordless position pointing device wherein a resonance circuit is installed in the position pointing device enabling cordless communication between a tablet and the position pointing device. An apparatus that operates easily is thus provided. U.S. Pat. No. 5,466,896, an improvement on said U.S. patent, further discloses a position detecting apparatus wherein plural position pointing devices are detected on the same tablet simultaneously by providing a distinct resonance frequency to each position pointing device. The disclosures of U.S. Pat. Nos. 4,878,553 and 5,466,896 are hereby incorporated by reference.
A conventional position detecting apparatus disclosed in the prior art, however, could detect plural position pointing devices on the same tablet only if different frequencies are assigned to resonance circuits in advance in order to avoid electromagnetic interference.
In general, a user does not have a conscious awareness of which position pointing device has a particular frequency. A user therefore often makes the mistake of picking up two position pointing devices which have the same frequency and tries to use them simultaneously.